The head injury criterion (HIC) is a measure of the likelihood of

head injury A head injury is any injury that results in trauma to the skull or brain. The terms ''traumatic brain injury'' and ''head injury'' are often used interchangeably in the medical literature. Because head injuries cover such a broad scope of inju ...

arising from an impact. The HIC can be used to assess safety related to vehicles, personal protective gear, and sport equipment. Normally the variable is derived from the measurements of an accelerometer mounted at the

center of mass In physics, the center of mass of a distribution of mass in space (sometimes referred to as the balance point) is the unique point where the weighted relative position of the distributed mass sums to zero. This is the point to which a force may ...

of a

crash test dummy A crash test dummy, or simply dummy, is a full-scale anthropomorphic test device (ATD) that simulates the dimensions, weight proportions and articulation of the human body during a traffic collision. Dummies are used by researchers, automobi ...

’s head, when the dummy is exposed to crash forces. It is defined as:

\mathit\mathit\mathit =  \max_ \bigg\

Head Injury Criteria and the ATB
/ref>

where ''t''₁ and ''t''₂ are the initial and final times (in seconds) chosen to maximize HIC, and

acceleration In mechanics, acceleration is the rate of change of the velocity of an object with respect to time. Accelerations are vector quantities (in that they have magnitude and direction). The orientation of an object's acceleration is given by the ...

''a'' is measured in ''g''s (

standard gravity The standard acceleration due to gravity (or standard acceleration of free fall), sometimes abbreviated as standard gravity, usually denoted by or , is the nominal gravitational acceleration of an object in a vacuum near the surface of the Earth. ...

acceleration). The time duration, ''t''₂ – ''t''₁, is limited to a maximum value of 36 ms, usually 15 ms. This means that the HIC includes the effects of head acceleration and the duration of the acceleration. Large accelerations may be tolerated for very short times. At a HIC of 1000, there is an 18% probability of a severe head injury, a 55% probability of a serious injury and a 90% probability of a moderate head injury to the average adult.

Automobile safety

HIC is used to determine the U.S.

National Highway Traffic Safety Administration The National Highway Traffic Safety Administration (NHTSA ) is an agency of the U.S. federal government, part of the Department of Transportation. It describes its mission as "Save lives, prevent injuries, reduce vehicle-related crashes" rela ...

(NHTSA) star rating for automobile safety and to determine ratings given by the

Insurance Institute for Highway Safety The Insurance Institute for Highway Safety (IIHS) is a U.S. nonprofit organization funded by auto insurance companies, established in 1959 and headquartered in Arlington, Virginia. It works to reduce the number of motor vehicle traffic collision ...

. According to the

, head injury risk is evaluated mainly on the basis of head injury criterion. A value of 700 is the maximum allowed under the provisions of the U.S. advanced airbag regulation (NHTSA, 2000) and is the maximum score for an "acceptable" IIHS rating for a particular vehicle. A HIC-15 (meaning a measure of impact over 15 milliseconds) of 700 is estimated to represent a 5 percent risk of a severe injury (Mertz et al., 1997). A "severe" injury is one with a score of 4+ on the Abbreviated Injury Scale (AIS) Data for specific vehicles can be found on various automotive review websites. Some sample data is as follows, for comparative purposes: * The 1998

Ford Windstar The Ford Windstar (later the Ford Freestar and Mercury Monterey) is a minivan that was produced and sold by Ford. The replacement for the Ford Aerostar, the Windstar adopted the front-wheel drive configuration of the Chrysler minivans. From the ...

, marketed as one of the safest minivans of that year, tested out to a HIC=305 score for driver * A small car, a 1998

Dodge Neon Dodge is an American brand of automobiles and a division of Stellantis, based in Auburn Hills, Michigan. Dodge vehicles have historically included performance cars, and for much of its existence Dodge was Chrysler's mid-priced brand above Ply ...

, tested at HIC=265. * A common family sedan, a 1998

Toyota Camry The Toyota Camry (; Japanese: トヨタ・カムリ ''Toyota Kamuri'') is an automobile sold internationally by the Japanese auto manufacturer Toyota since 1982, spanning multiple generations. Originally compact in size (narrow-body), the Camry ...

, tested at HIC=288. * A 2007 Camry at HIC=175. A comprehensive searchable database of vehicles and their HIC scores is available a
safercar.gov

Athletics and recreation

Sport physiologists and

biomechanics Biomechanics is the study of the structure, function and motion of the mechanical aspects of biological systems, at any level from whole organisms to organs, cells and cell organelles, using the methods of mechanics. Biomechanics is a branch of ...

experts use the HIC in the research of safety equipment and guidelines for competitive sport and recreation. In one study,

concussion A concussion, also known as a mild traumatic brain injury (mTBI), is a head injury that temporarily affects brain functioning. Symptoms may include loss of consciousness (LOC); memory loss; headaches; difficulty with thinking, concentration, ...

s were found to occur at HIC=250 in most athletes. Studies have been conducted in skiing and other sports to test adequacy of helmets Head Injury in Snowboarding: Evaluating the Protective Role of Helmets
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References

{{reflist

External links

Use of Head Injury Criterion in Crash Test RatingsInjury Measurements and CriteriaSaving Lives with Impact Protection Product
Automotive safety Neurotrauma Mathematical modeling

Automobile safety

Athletics and recreation

See also

References

External links